1. Field of the Invention
The present invention relates to wind turbines. More particularly, the invention relates to fiber optic safety system for such wind turbines.
2. Prior Art
A typical safety system for a wind turbine may include a series of switches connected to Emergency Feather Command (EFC) relays in Blade Pitch Controller (BPC). Emergency stop buttons, hub lock switches, over-speed sensors, and watchdog timers may be connected in a series loop. The loop may also include other items required to provide proper equipment and personnel safety during failure modes. Therefore, if any of these buttons, switches, and/or sensors in the loop is open, aerodynamics is applied to pitch the turbine blades into a 90-degree feathered position, and/or mechanical braking to stop the turbine rotation. The safety system further includes stored energy source, such as a battery, that enables blade pitch to occur after a loss of power.
The series loop may originate from the up-tower (referred to as a nacelle) or the down-tower controller. In either case, electrical wires connect the safety system between the down-tower controller and the up-tower controller, including the Blade Pitch Controller. However, the electrical connection between the down-tower and up-tower controllers may be adversely affected by common mode noise, such as electrical and/or electromagnetic interferences. Furthermore, the interferences may also affect the overall control system because of the noise induction into the power supply.
The present invention, in one aspect, describes a fiber optic safety system for a wind turbine. The system includes a series of switching elements coupled together to indicate a fail-safe condition of the wind turbine. The system also includes a plurality of optical transceivers, a plurality of optical conductors, and a blade pitch controller. The optical transceivers are coupled to the series of switching elements. Moreover, each of the optical transceivers is disposed at least at a down tower and an up tower of the wind turbine. The optical conductors are then coupled to the optical transceivers to carry optical signals between the down tower and the up tower. The blade pitch controller is connected to an up-tower optical transceiver, where the controller controls wind turbine blades.
In another aspect, the present invention describes a method to optically monitor safety condition of a wind turbine. The method includes monitoring a state of safety switches. Optical signals are then transmitted between an up tower and a down tower as a result of the state of safety switches. The wind turbine blades are pitched to desired positions when the optical signals indicate a safe condition. Otherwise, when the optical signals indicate a fail condition, the wind turbine blades are pitched into a feathered position.